Writing instrument for low-viscous ink without an absorbing fibrous bundle

ABSTRACT

Writing instrument comprising a pen tip, a reservoir containing low-viscous ink, an ink feeding conduit extending from the pen tip into the reservoir and having an inner ink passageway extending therethrough, an air admission inside tube covering the conduit, with an annular air passage formed therebetween to permit a capillary action therein, and an air admission outside tube covering the inside tube, with a large space formed therebetween, and having an air port in its rear portion. The conduit is formed in its peripheral wall with a port positioned in the front end of the reservoir to permit the ink passageway to communicate with the interior of the reservoir. The opposite ends of the outside tube are closed, while the annular air passage has a front end open to the front portion of the outside tube and a rear end open to the front end of the reservoir, whereby the ink in the reservoir is rendered replaceable by air.

United States Patent 11 1 Yoshida 51 Mar. 25, 1975 WRITING INSTRUMENTFOR LOW-VISCOUS INK WITHOUT AN ABSORBING FIBROUS BUNDLE [75] Inventor:Kisaburo Yoshida, Osaka, Japan [73] Assignee: Kabushiki KaishaSakurakurepasu,

Osaka, Japan [22] Filed: Apr. 3, 1973 [21] Appl. No.: 347,465

[30] Foreign Application Priority Data Apr. 26, 1972 Japan 4742508 [52]US Cl. 401/292, 401/209 [51] Int. Cl B43k 5/00 [58] Field of Search401/292, 198, 199, 223, 401/224, 134, 209, 261

[56] References Cited UNITED STATES PATENTS 3,338,216 8/1967 Roller401/292 X 3,361,516 1/1968 Rigondaud 401/292 3,501,225 3/1970 Martin eta1. I 401/198 3,614,248 10/1971 Otsuka 401/292 3,687,561 8/1972 Phillips401/292 FOREIGN PATENTS OR APPLICATIONS 422,575 4/1967 Switzerland401/198 swam? Primary E.\'aminer-Lawrence Charles Atlorney, Agent, orFirmLarson, Taylor and Hinds [57] ABSTRACT Writing instrument comprisinga pen tip, a reservoir containing low-viscous ink, an ink feedingconduit extending from the pen tip into the reservoir and having aninner ink passageway extending therethrough, an air admission insidetube covering the conduit, with an annular air passage formedtherebetween to permit a capillary action therein, and an air admissionoutside tube covering the inside tube, with a large space formedtherebetween, and having an air port in its rear portion. The conduit isformed in its peripheral wall with a port positioned in the front end ofthe reservoir to permit the ink passageway to communicate with theinterior of the reservoir. The opposite ends of the outside tube areclosed, while the annular air passage has a front end open to the frontportion of the outside tube and a rear end open to the front end of thereservoir, whereby the ink in the reservoir is rendered replaceable byair.

7 Claims, 6 Drawing Figures amaze:

PATENTEDHARZSISYS felllallllllfil sum 1 or z PATENTEUHARZWYB 3.873.218sum 2 o 2 FIG 5 BACKGROUND OF THE INVENTION The present inventionrelates to writing instruments such as marking pens and ball-point penshaving a reservoir which contains aqueous ink, alcoholic ink or likelow-viscosity ink without using a conventional fibrous bundle.

With conventional writing instruments using aqueous ink oralcoholcontaining ink, ink inevitably flows out in a drop or to excessduring writing when the amount of outflow of ink undergoes minutevariations due to changes in the atmospheric pressure and temperature.This is the most serious problem heretofore encountered with writinginstruments of the above-mentioned type, unlike those for use withhigh-viscosity ink such as ball-point pens for oily ink. For example,the body temperature is transmitted during writing from the fingers tothe pen barrel to expand the air or ink in the pen barrel, therebycausing excess outflow of ink from the pen tip or from variousclearances in the ink channel. In order to avoid such trouble,conventional marking pens employ a fibrous bundle for absorbing andretaining ink. However, the amount of ink contained in the pen barrel asabsorbed by the fibrous bundle is extremely limited and, moreover, onlyabout 50% of the total amount of the ink is actually usable for writing.Furthermore, the known structure fails to assure sufficient flow of inkfor rapid writing. Consequently, the pen of the type described readilyruns short of ink and is serviceable only for a very short period oftime. It is also known that usual fountain pens have a nib supportelement formed with several flutes for preventing excess outflow of ink.It is, however, impossible to incorporate such element into a markingpen or ballpoint pen.

SUMMARY OF THE INVENTION It is therefore a main object of this inventionto provide a writing instrument for low-viscosity ink including astructure in which an ink reservoir containing a large amount of inkwithout employing a fibrous bundle communicates with the atmosphere freeof any leakage of ink and which is capable of automatically replenishingthe reservoir with air at a rate corresponding to the consumption ofink, the structure further being such that even in the event of a changein temperature or atmospheric pressure, expanded air or ink in thereser-' voir can be released through an opening other than the inkpassageway while keeping the ink in the passageway free of any influenceso as to eliminate any excess outflow of ink and to ensure smooth flowof ink at a constant rate all the time for a prolonged period.

Another problem encountered with writing instruments for use withlow-viscosity ink is that bubbles are likely to be formed in the inkpassageway and, once formed, they interfere with capillary action withinthe passageway, rendering the instrument no longer serviceable.

Accordingly, a further object of this invention is to provide a writinginstrument for low-viscosity ink in which formation of bubbles in theink passageway is prevented and bubbles, even if formed, will notcompletely impede the flow of ink through the passageway, making itpossible to use the whole amount of ink in the reservoir without leavingany droplet of ink.

Other objects and features of the present invention will become moreapparent from the following description of preferred embodiments of theinvention with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectionalview ofa writing instrument embodying the present invention;

FIG. 2 is an enlarged view in section taken along the line A-A of FIG.I;

FIG. 3 is an enlarged fragmentary perspective view showing an inkfeeding conduit partly broken away;

FIG. 4 is a longitudinal sectional view showing another embodiment ofthis invention;

FIG. 5 is a longitudinal sectional view showing another embodiment ofthis invention; and

FIG. 6 is an enlarged view in section taken along the line B-B of FIG.5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The writing instrumentof this invention for a lowviscosity ink basically comprises a reservoir1 which contains a large amount ofink without an ink absorbing fibrousbundle, a pen tip 2, and an ink feeding conduit 3 connecting thereservoir 1 to the pen tip 2 so that ink 4 within the reservoir 1 is fedto the pen tip 2 by the capillary action of the ink feeding conduit. Theinstrument of this invention is characterized by a structure forsubstituting air for ink by which the ink reservoir is automaticallyreplenished with an amount of air corresponding to the consumption ofink. This structure for substituting air for ink will first be describedin detail.

An air admission inside tube 5 and an air admission outside tube 6 areusually molded of synthetic resin and cover the ink feeding conduit 3extending between the front end of the reservoir 1 and the pen tip 2.The air admission outside tube 6 has a connecting portion 7 at its backend, a constricted portion 8 at the front end thereof, and a port 9 at arear portion thereof. The reservoir l is tightly fitted around theconnecting portion 7, and the constricted portion 8 firmly holds the inkfeeding conduit 3. The air admission inside tube 5 is smaller indiameter than the air admission outside tube 6. Between the innerperipheral surface of the inside tube 5 and the outer peripheral surfaceof the outside tube 6, there is formed a very small annular clearance 10as an air passage, such that when the ink is introduced into the airpassage 10, a powerful capillary action will be produced therein. Theinside tube 5 has a thick back end 11 which is tightly fitted in theback end of the air admission outside tube 6, thereby keeping the backend of the air passage 10 open to the front end of the reservoir 1. Thefront end of the annular passage 10 is open to the inner front portionof the air admission outside tube 6. The clearance between the airadmission inside tube 5 and the air admission outside tube 6 is formedas widely as possible so that ink will not be drawn by capillary actionfrom the front portion to the rear portion of the air admission outsidetube 6 even if a small amount of ink is deposited in the front portionof the tube 6.

Various types of the ink feeding conduit 3 and the pen tip 2 will now bedescribed in detail.

FIGS. 1 to 3 show an ink feeding conduit 3a made of a wear resistantmaterial such as acetal resin and having a very fine ink passageway 12which is accurately diseen in cross section, the passageway 12 comprisesa plurality of radial channels P each of which is tapered toward thecenter Q of the conduit 3a in the form of an elongated isoscelestriangle, the channels P communi eating with one another at theirvertexes, i.e., at the center Q. The shape of the ink passageway 12 isnot limited to that shown but the passageway may be of any shape insofaras it has a very small clearance which will induce a very effectivecapillary action, such that bubbles, if any in the ink, will not blockup the passageway 12 to interrupt the flow of ink through the passageway12. Thus the constituent channel or the passageway must at least benoncircular in cross section. Especially in the case where thepassageway 12 comprises a plurality of channels P which are in the formof an isosceles triangle and which communicate with one another at thecenter Q as in the present embodiment, the ink will be drawn toward anarrower portion. Consequently the ink flows three-dimensionally, i.e.,in the axial direction and from the peripheral portions of thepassageway toward the center in a plane perpendicular to the axialdirection. This is the most preferable mode of supply of ink to thecenter of the pen tip. The ink feeding conduit 3 extends from a rearportion of the reservoir l to the pen tip 2 coaxially with the airadmission inside tube 5 and the air admission outside tube 6. A port 13for releasing air and admitting ink is formed in the peripheral wall ofthe ink feeding conduit 3, at a position in the front end of thereservoir 1. The port 13 communicates with the ink passageway 12 andserves to release air (bubbles) from the passageway 12. Through the port13, the ink in the front portion of the reservoir 1 is introduced intothe passageway by the capillary action and vacuum of the interior of thepassageway during writing. As a rule, the air and ink port 13 ispositioned only in the front end of the reservoir 1. However, anotherport may be formed in a portion of the conduit corresponding to themidportion or rear portion of the reservoir 1. An auxiliary air and inkport 14 formed in the peripheral wall of the ink feeding conduit 3 ispositioned in the front end of the air admission outside tube 6, and hassubstantially the same function as the aforementioned air and ink port13 in the reservoir 1 except that whereas the air and ink port 13 takesin the ink within the reservoir 1, the auxiliary air and ink port 14draws in the ink collected in the front portion of the air admissionoutside tube 6. More specifically although the ink which has flowed intothe air passage is usually retained therein by surface tension since theair passage 10 is in the form ofaminute clearance, some ink in the airpassage 10 may possibly be deposited in the front portion of the airadmission outside tube if the pen is left unused with its tip down. Whenthe pen is then put to use, the ink is withdrawn from the front portioninto the conduit 3 through the port 14. The writing instrument isoperable free of any trouble without the auxiliary port 14, butexperiments have revealed that the provision of the auxiliary port 14permits the writing instrument to display superior performance.

The tip 2a shown in FIG. 1 is formed by cutting the end of the inkfeeding conduit 3a into a conical shape. The ink passageway inside theconduit 3a is therefore exposed on the conical surface of the inkfeeding conduit 3a, and ink flows through the ink passagewayconcentrically to the center 0 at the pen tip 2a.

The ink feeding conduit 3a in FIG. 4 has the same construction as thatillustrated in FIGS. 1 to 3. As in the foregoing embodiment, the inkpassageway 12 therein is not limited to the shape in which channels arearranged radially in cross section but may be of any cross sectionalshape other than circular form insofar as the passageway will induce aneffective capillary action and will not be blocked up with bubbles. Thepen tip 2b of FIG. 4 comprises a ball-point pen tip 16 of metal orsynthetic resin fitted around the front end of the ink feeding conduit3a. The ball-point pen tip has a ball 15 in its top. The end surface ofthe ink feeding conduit 3a serves to seat the ball 15. The ball-pointpen tip may be of any construction if ink can be transferred from thefeeding conduit onto paper.

The ink feeding conduit 3b in FIG. 5 comprises a slender tube 17 andseveral smooth-surfaced linear elements 18 such as nylon wires orstainless steel wires inserted in the tube 17 and extending over theentire length of the tube 17 to provide an ink passageway 19 in the formof minute clearances between the linear elements l8 and the peripheralinner surface of the tube 17 and amongst the linear elements themselves.In other respects, this ink feeding conduit 3b is identical to the inkfeeding conduit 30 shown in FIG. 1. The pen tip 20 in FIG. 5 comprises aball-point pen tip 21 made of metal or synthetic resin and having a ball20 in its top end and a rear portion 22 receiving the ink feedingconduit 3b. A small bore 23 is formed in the front portion of the tip21. A single element 18' among the linear elements 18 within the inkfeeding conduit 36 is inserted in the small bore 23, with the end of theelement 18' in contact with the ball 20. During writing, the rollingball 20 shakes the linear element 18' in contact therewith, therebyfeeding ink from the conduit 3h onto the ball 20.

In FIGS. 4 to 6, indicated at 24 is a pen barrel and at 25, an air portformed in a suitable portion of the pen barrel 24. The reservoir 1 andthe air admission outside tube 6 need not always be covered with the penbarrel 24. Where an elongated reservoir is used and connected to theoutside tube, the assembly serves as a pen barrel. In the drawings,theparts referred to by the same reference numerals and characters havethe same construction and function in the same manner.

The reservoir 1 may be of the interchangeable or disposable cartridgetype or may be adapted for replenishment.

When the reservoir 1 filled with ink is tightly fitted to the connectingportion 7 of the air admission outside tube 6, the ink 4 isinstantaneously introduced into the ink feeding conduit 3a or 312 fromits rear end as well as through the air and ink port 13 and is fed tothe pen tip 2a, 212 or 26 by powerful capillary action of the inkpassageway 12 or 19, while permitting air to escape from the inkpassageway 12 or 19 through the air and ink port 13, auxiliary port 14,and pen tip. Even if air should remain in the ink passageway 12 or 19,the air is in the form of fine bubbles and will not block up the entirecross sectional area of the passageway 12 or 19, since the passageway 12comprises radially arranged channels and is not circular in crosssection, whilst the passageway 19 comprises clearances among severallinear elements 18. Thus the bubbles will in no way interrupt the flowof ink, permitting effective capillary action. When air is introducedinto the ink feeding conduit 3a or 3b during writing, the conduitsimilarly functions effectively to assure satisfactory capillary action.Inasmuch as the ink passageway 12 or 19 comprises minute channels orclearances as described above, the ink fed to the pen tip 2a, 2b or 2cis effectively retained in the ink passageway 12 or 19 by virtue of highsurface tension when the pen is not in use. Furthermore, ink 4 is alwayskept in contact with the inlet of the ink feeding conduit 3a or 312whether the pen is left for a long time in horizontal position or inupright position with its tip up, because the conduit 3a or 3b extendsto the back end of the reservoir 1 and has the air and ink port 13positioned in the front end of the reservoir 1. Thus the pen tip 2a, 212or is wet with the ink all the time, ready for writing.

When the pen is put to use for writing, the friction of the pen tip 20,2b or 2c with paper and the ability of paper to absorb ink cause the inkto continuously flow out of the ink passageway 12 or 19 toward the pentip, whilst the vacuum and capillarity in the interior of the inkfeeding conduit 30 or 3b force the ink in reservoir 1 to flow into thepassageway 12 or 19 from the rear end and/or the air and ink port 13 ofthe conduit. At a rate corresponding to the consumption of ink, air issupplied to the reservoir 1 from an air port of the pen barrel 24,through the port 9 of the air admission outside tube 6 and then throughthe annular passage of the air admission inside tube 5. Thussubstitution of air for ink can be effected smoothly.

The air passage 10 of the air admission inside tube 5 plays an importantrole in the foregoing operation. That is to say, during writing with thepen tip down, some of ink 4 flows into the annular passage 10 from itsopen rear end, but the annular passage which is in the form of thesmallest possible clearance permits a high surface tension to act toeffectively retain the ink therein. Consequently, hardly any ink willflow out into the air admission outside tube 6. When the writinginstrument is used, with the ink effectively retained within the annularpassage 10, a vacuum is created in the reservoir 1, whereby air isintroduced in the form of fine bubbles into the ink in the passage 10 byway of the ports already described and is eventually withdrawn into thereservoir 1 together with the ink.

Thus although the annular passage 10 is open to the front end of thereservoir 1, the passage 10 which is a small clearance enables a highsurface tension to act to retain the ink within the passage 10, withoutallowing hardly any ink to flow into the outside tube 6 even if the penis shaken forcibly. During writing, the vacuum produced in the reservoirdraws air through the tube 6 into the reservoir in the form of finebubbles along with the ink held in the annular passage 10. In this way,the ink in the reservoir can be replaced by air without any troublenotwithstanding that the annular passage 10 is blocked with ink.Although the air passage 10 at the front end of the reservoircommunicates with the atmosphere, the annular passage functions toassure substitution of air for ink without permitting ink to leak out.This is the most distinct feature of this invention.

Furthermore, even if some of ink retained in the passage 10 should bedeposited in the front portion of the air admission outside tube 6, theink will be drawn into the ink feeding conduit 3a or 3b during writing,if the anxiliary air and ink port 14 is formed in the conduit at thatposition.

The air in the reservoir may expand due to changes in temperature oratmospheric pressure, but some air can be released through the annularpassage 10, thereby preventing excess outflow of ink. For the samereason, insufficient flow of ink can be avoided in the event ofcontraction of air in the reservoir.

The air and ink port 13 formed in the ink feeding conduit 3a or 3b andpositioned in the front end of the reservoir 1 makes it possible to useup the ink in the reservoir without leaving almost any droplet of ink.

I claim:

1. A writing instrument for low-viscous ink comprising a pen tip, areservoir containing said ink without employing an ink absorbing fibrousbundle, an ink feeding conduit extending from said pen tip into saidreservoir to its rear portion and having an inner ink passagewayextending throughout the entire length thereof, said conduit having inits peripheral wall a port positioned in the front end ofsaid reservoirand permitting said ink passageway to communicate with the interior ofsaid reservoir, an air admission inside tube covering said conduit andforming an annular air passage between the inner peripheral surface ofsaid air admission inside tube and the outer peripheral surface of saidconduit which annular passage permits capillary action therein, an airadmission outside tube covering both said conduit and said inside tubeand being closed at its opposite ends so that a sufficiently large spaceis formed between said inside and outside tubes to prevent ink frombeing drawn by capillary action from the front portion of said outsidetube toward its rear por tion, said air admission outside tube having inits rear portion an air port for permitting the interior of said airadmission outside tube to communicate with the atmosphere, said annularair passage having a front end open to the front portion of said outsidetube and a rear end open to the front end of said reservoir, whereby theink in said reservoir is rendered replaceable by air.

2. A writing instrument for low-viscous ink according to claim 1, inwhich said ink passageway comprises a plurality of channels radiallyarranged in cross section and communicating with each other at thecenter of the passageway.

3. A writing instrument for low-viscous ink according to claim 2, inwhich said ink feeding conduit is made of synthetic resin.

4. A writing instrument for low-viscous ink according to claim 3, inwhich the front end of said ink feeding conduit is conically cut toserve as said pen tip.

5. A writing instrument for low-viscous ink according to claim 4, inwhich said ink feeding conduit has a port formed in the peripheral wallthereof and positioned in the front end of said air admission outsidetube, the ink passageway communicating with the space between saidinside and outside tubes through said port.

6. A writing instrument for low-viscous ink according to claim 5, inwhich the front end of said ink feeding conduit has a ball-point pen tipfitted therein and serving as said pen tip.

7. A writing instrument for low-viscous ink according to claim 1 inwhich several linear elements are inserted into the ink feeding conduit,said ink passageway comprising the clearances among said linearelements, and the front end of said conduit has a ball-point pen tipserving as said pen tip.

1. A writing instrument for low-viscous ink comprising a pen tip, areservoir containing said ink without employing an ink absorbing fibrousbundle, an ink feeding conduit extending from said pen tip into saidreservoir to its rear portion and having an inner ink passagewayextending throughout the entire length thereof, said conduit having inits peripherAl wall a port positioned in the front end of said reservoirand permitting said ink passageway to communicate with the interior ofsaid reservoir, an air admission inside tube covering said conduit andforming an annular air passage between the inner peripheral surface ofsaid air admission inside tube and the outer peripheral surface of saidconduit which annular passage permits capillary action therein, an airadmission outside tube covering both said conduit and said inside tubeand being closed at its opposite ends so that a sufficiently large spaceis formed between said inside and outside tubes to prevent ink frombeing drawn by capillary action from the front portion of said outsidetube toward its rear portion, said air admission outside tube having inits rear portion an air port for permitting the interior of said airadmission outside tube to communicate with the atmosphere, said annularair passage having a front end open to the front portion of said outsidetube and a rear end open to the front end of said reservoir, whereby theink in said reservoir is rendered replaceable by air.
 2. A writinginstrument for low-viscous ink according to claim 1, in which said inkpassageway comprises a plurality of channels radially arranged in crosssection and communicating with each other at the center of thepassageway.
 3. A writing instrument for low-viscous ink according toclaim 2, in which said ink feeding conduit is made of synthetic resin.4. A writing instrument for low-viscous ink according to claim 3, inwhich the front end of said ink feeding conduit is conically cut toserve as said pen tip.
 5. A writing instrument for low-viscous inkaccording to claim 4, in which said ink feeding conduit has a portformed in the peripheral wall thereof and positioned in the front end ofsaid air admission outside tube, the ink passageway communicating withthe space between said inside and outside tubes through said port.
 6. Awriting instrument for low-viscous ink according to claim 5, in whichthe front end of said ink feeding conduit has a ball-point pen tipfitted therein and serving as said pen tip.
 7. A writing instrument forlow-viscous ink according to claim 1 in which several linear elementsare inserted into the ink feeding conduit, said ink passagewaycomprising the clearances among said linear elements, and the front endof said conduit has a ball-point pen tip serving as said pen tip.